The increase in circuit density and operating frequency of integrated circuits and multi-chip modules utilized in present day computer systems has resulted in an exponential increase in the power dissipated by those components. For example, just a few years ago the maximum power generated by a typical complementary metal oxide semiconductor (CMOS) central processor unit (CPU) utilized within a personal computer was in the neighborhood of two watts. Currently, the Intel Corporation Pentium.TM. processor dissipates an estimated sixteen watts, and the next generation Intel Corporation processor is estimated to generate near thirty watts. Cooling arrangements must be provided to prevent damage to these integrated circuits from the high temperatures generated by the devices.
In addition to cooling to prevent damage resulting from overheating, it is known that a CMOS circuit will operate at higher clock speeds as the circuit temperature is lowered. In some cases the processor frequency of CMOS processor has been improved to near 300% through the cooling of the processor die to a temperature of approximately -200.degree. C. Many methods for sub-cooling processors and other computer components are known. One such cooling system comprises a plurality of hollow cold plates which are attached to the processors, modules or other components to be cooled. A liquid coolant is circulated from a refrigeration unit through connecting conduits to the cold plates to effectuate cooling of the attached components. Other known cooling methods include directing a cooling airflow onto components requiring cooling, sealing the computer cabinetry and refrigerating the interior of the cabinet, immersing components in a coolant such as liquid nitrogen, or interfacing components with a Peltier TEC (thermal electric cooling) device.
Cooling of components to a temperature less than the local dew point presents certain difficulties in that condensation may form on the cold elements of the cooling system, such as the conduits, cold plates, sub-cooled components and structures to which the elements of the cooling system or the sub-cooled components are attached. This condensation can cause temporary or permanent damage to electrical components within the computer system.
One solution to this condensation problem is to surround the sub-cooled components with appropriate insulation. Unfortunately, providing insulation around cooling system elements and sub-cooled components increases the minimum distance between components and complicates computer component arrangement and cabinet design.
Increasing the distance between components is contrary to the desire of designers to minimize the distance between components within high frequency computing systems to provide appropriately short signal propagation paths. Of particular concern is the close spacing between printed circuit boards which are plugged into a common printed circuit backpanel which serves as a system bus. Short signal transmission paths are required to prevent undesirable transmission line effects and improve total system throughput.
In a sub-cooled computing system, the need for minimizing signal path lengths and component spacing precludes the use of appropriately thick insulators between printed circuit boards or other sub-cooled components that is required to prevent the formation of condensation.